In a method for testing the measurement accuracy of magnetic field sensors that is known in actual practice, a wafer that contains a plurality of semiconductor chips in the form of magnetic field sensors in which a Hall effect sensor circuit is integrated is prepared. The individual semiconductor chips each have electrical connection contacts that can be connected to matching contacts on a test instrument. The semiconductor chips are positioned one after another on an exciter coil, which is supplied with a specified current by means of a current source in order to generate a reference magnetic field. The semiconductor chip that is located on the exciter coil is connected by means of the connection contacts to the matching contacts of the test instrument in order to supply current to the semiconductor chip and to acquire a measured value for the magnetic flux density in the reference magnetic field and to transfer it to the test instrument. In the test instrument the measured value is compared with a specified reference value range. The reference value range is specified as a function of the specified magnetic flow density in the reference magnetic field and the measurement accuracy required for the Hall effect sensor. If a deviation between the measured value and the reference value range occurs, the Hall effect sensor in question is marked with a colored dot. After the Hall effect sensors that are located on the wafer have been tested in this way, the semiconductor chips are singulated by dividing the wafer along predefined scribe lines running between the semiconductor chips. The marked semiconductor chips are culled out as defective. The remaining semiconductor chips are connected by means of bond wires to the contact lugs provided on a lead frame and are then surrounded by a plastic housing in such a way that the free ends of the contact lugs extend out of the plastic. With the aid of the contact lugs, the resulting magnetic field sensors may be soldered, for example, to the lead tracks of a circuit board.
This method has the disadvantage that the testing of the measurement accuracy of the magnetic field sensors is subject to a series of factors that can cause errors that limit measurement accuracy. For example, the current in the exciter coil and therefore the magnetic flux density of the reference magnetic field can deviate from a specified value due to temperature variations in the power source and/or in the exciter coil. In addition, because of positioning tolerances the individual semiconductor chips may be located at different distances from the exciter coil when they are positioned at the exciter coil. The magnetic field sensors that are tested by means of this method therefore have relatively wide tolerances. In safety-related applications, such as magnetic field sensors to report the position of a butterfly valve in an internal combustion engine to an electronic engine control unit, however, very tight measured value tolerances are required, and these tolerances cannot be maintained with this method, or they can only be achieved at very great effort and expense.